Spermatogenesis will be used as a model system to study the role of cellular oncogenes during different stages of cell division (mitosis and meiosis) and cell differentiation. Work is being initiated to study the expression of different oncogenes both at the transcriptional level, using specific oncogene DNA probes, and at the protein level, using antisera against viral or cellular oncogene products. Efforts will be made to analyze molecular mechanisms involved in the expression of oncogenes and their putative role in carrying out normal cellular functions. The constitutive expression of human-myc (Hu-myc) oncogene products, using mammalian expression vector systems and formation of stable cell lines, over-producing Hu-myc, are being established. Hu-myc DNA fragment containing entire coding sequences (three exons) or part of it (second and third exons), have been cloned into a transient expression vector (t25) or into a protein secretion expression vector system. Work is in progress to identify putative Hu-myc transcripts and polypeptides obtained after transfection of these hybrid constructs into CV-1 cells. Based on these results, appropriate constructs will be chosen to form stable cell lines to overproduce Hu-myc-proteins, using metallothioneinbovine papilloma virus-hybrid (MT-BPV) vectors. Biological functions of Hu-myc proteins and its role in cell differentiation, cell proliferation will be assessed.